With rapid growth of traffic, bit rates of optical signals transmitted in a wavelength division multiplexing (WDM, Wavelength Division Multiplexing) network are higher and higher. In the near future, the bit rates of transmitted optical signals will be up to 400 Gbit/s (4×1011 bit/s) or even 1 Tbit/s (1×1012 bit/s). An optical network that uses a spectrum grid of a fixed width to transmit optical signals is called a fixed bandwidth optical network, and an optical network that uses spectrum grids of different widths to transmit optical signals is called a variable-bandwidth optical network. In this way, in a variable-bandwidth optical network, when the spectrum width of an optical signal is large, the spectrum of an optical signal may occupy multiple optical frequency slots (OFS, Optical Frequency Slot). In the present invention, an OFS refers to a spectrum resource of a minimum spectrum width in the optical network as far as a spectrum can be divided, that is, a minimum spectrum unit in the optical network as far as the spectrum can be divided.
An optical signal may be carried in a continuous spectrum region, or may be carried in separated spectrum regions. That is, an optical signal may occupy several continuously concatenated OFSs or occupy several separated OFSs.
In the prior art, management or control for transmission of optical signals is implemented by using a 32-bit wavelength identifier (Wavelength ID). A format of the wavelength identifier is given in Table 1:
Wavelength ID (32 bits)0 12345678910111213141516171819202122232425262728293031GridChanneln (16 bits)Reserved(3 bits)spacing(4 bits)
In the foregoing table, the field Grid indicates whether the grid is a dense wavelength division multiplexing (DWDM, Dense Wavelength Division Multiplexing) grid or a coarse wavelength division multiplexing (CWDM, Coarse Wavelength Division Multiplexing) grid; the field Channel spacing indicates the type of a selected spectrum grid, for example, 100 GHz spacing, 50 GHz spacing, 25 GHz spacing, and so on; and the field n is used to calculate a nominal central frequency of an optical signal, that is, the field n indicates the nominal central frequency of the optical signal. The field Reserved is a reserved field.
However, the management or control for transmission of optical signals does not consider the application of a variable-bandwidth network, that is, does not consider a case where an optical signal may occupy multiple OFSs, and cannot identify spectrum information of the optical signals that have such characteristics. In the prior art, there is another method for controlling and managing transmission of optical signals. Considering that an optical signal may occupy multiple OFSs, the method defines the wavelength identifier as follows:
1) The definitions of the field Grid and the channel spacing field are basically unchanged.
2) The field n is modified to a field that indicates a nominal central frequency corresponding to a lowest-frequency OFS occupied by a signal but no longer indicates the nominal central frequency of the entire signal.
3) The first three bits of the field Reserved are modified to “extra-slots” to support the number of OFSs occupied by the signal, and the remaining 6 bits are still reserved.
The inventor of the present invention finds that in the prior art, the field n defines the lowest-frequency OFS occupied by the signal, and the field Reserved is used to define the number of OFSs occupied by the signal. However, according to this method, the optical signal can occupy only 8 OFSs, and the case where the optical signal occupies more OFSs cannot be described accurately. In extreme cases, assuming that one signal can select the OFS (using 6.25 GHz as a unit) at a C band arbitrarily, at most about 640 OFSs can be selected. In the case where an optical signal can occupy only several continuously concatenated OFSs, 10 bits are required, which is not supportable in the prior art. In addition, in a case where an optical signal can occupy several separated OFSs, the OFSs occupied by a signal need to be described completely, and 640 bits that amount to 80 bytes are required (using 6.25 GHz as a unit), which is excessive and far beyond the scope that can be described by the field Reserved. Such a manner of expressing the OFSs occupied by the signal is excessively cumbersome, and the management and control overhead is excessively large. In addition, in the prior art, the case that an optical signal is transmitted over different fibers cannot be handled.